The invention relates to an electromotive furniture drive, comprising a power supply device for adjusting movable furniture components relative to one another.
Such electromotive furniture drives are known in various embodiments. They are implemented as linear drives having a linearly adjustable output element or as rotational drives having a rotating output element and have proven themselves extremely well in practice. The linear drives have one or a number of electric motors, wherein a speed reduction gear is connected downstream of each motor and a further gear in the form of a threaded spindle gear for example is connected downstream of the speed reduction gear, which further gear generates a linear movement of the output element from the rotational movement of the motor. The rotational drives have at least one speed reduction gear connected downstream of the respective electric motor, wherein the last gearing element forms the output element. The output element of the respective electromotive furniture drive is connected to a fixed furniture component and/or to a movable furniture component, so that the movable furniture components are adjusted relative to one another during operation of the electric motor. The furniture can be implemented as a slatted frame, worktable, bed, reclining surface, treatment couch, hospital or healthcare bed, and also as a lifting device for persons such as lifters or patient lifters.
Switched-mode power supplies have shown excellent performance as power supply devices in the operation of the electromotive furniture drives. The power supply device has different operating states, i.e. an off operating state when disconnected from the mains, a start-up operating state until regular operation after connection to the mains, and an operational operating state in regular operation. The switched-mode power supplies comprise an isolating transformer switched by a control module with high frequency, which isolating transformer can also be designated as a transformer or a high-frequency transformer which is switched on and off by an upstream semiconductor switch on the primary side with a high switching frequency. For this purpose, a separate intermediate current circuit is associated with the control module which comprises an energy source of the control module and supplies the control module with electrical power.
If the power supply device is not connected to the mains or at least not for a period of time, the power supply device is in the “off” operating state, wherein all energy storage means such as capacitors for example are practically powerless. If the power supply device is connected to the mains, the operating state changes at first from the “off” operating state to the “start-up” operating state. The power source of the control module is connected to a charging circuit and supplies the power source in the start-up operating state with electrical power. Such an energy source with an associated charging circuit is known from the state of the art and has proven its excellence.
The state of the art of the mains disconnection device will be explained in closer detail, wherein the mains disconnection device comprises at least one switch controlled on the mains side in form of a relay switch or a semiconductor switch for disconnection from the mains. In the non-excited state of the mains disconnection device, the at least one controlled switch is in an open state and does not conduct any mains voltage to the power supply device. If the user operates a button on manual control, the mains disconnection device switches from the non-excited state to the excited state, wherein the controlled switch or the contacts of the controlled switch change to a closed state, wherein the power supply device is supplied with electrical power from the mains.
The mains disconnection devices have proven their excellence in practice, since they produce electrical isolation resp. disconnection from the mains and do not have any electrostatic alternating field at the output in the “isolation” resp. “disconnected” state. The costs are far from irrelevant however and the mounting effort is respectively high, since the mains disconnection devices are preferably arranged in a housing with attached mains plug.